Assembly for transmitting electrical signals and/or energy

ABSTRACT

An arrangement for transmitting electrical signals and/or energy between units mobile relative to each other, by means of galvanic contacts and a sliding-contact arrangement in particular. The inventive device excels itself by the provisions that at least one of said contacts comprises a basic material having a high mechanical stability, into which a second material is embedded which presents good electrical characteristics with respect to the transmission of electrical signals and/or energy, and that said second material is so distributed in said basic material that at least one further contact, which contacts this contact, is in contact with said second material along the major part of the trajectory of the movement.

FIELD OF THE INVENTION

The present invention relates to an arrangement for transmittingelectrical signals and/or energy between units mobile relative to eachother, by means of a sliding contact arrangement.

PRIOR ART

For the transmission of electrical signals between units mobile relativeto each other, sliding contacts are preferably employed. For linearmovement, these contacts are also known by the term slideways, whereasfor circular movement they are known as slip rings.

Such mechanical contact systems excel in simplicity and high sturdiness.For different applications, different contact pairings are available,which are selected based upon environmental conditions, contacting rate,and the electrical signals. When in the case of high contacting rates orhigh rotational speeds in the case of slip rings, a long service life isrequired and contact pairings are employed almost exclusively where atleast one contact contains a combination of silver and graphite. In thiscombination, the silver is utilized to produce good electrical contactwhile the graphite serves lubricating purposes.

As has been demonstrated in tests, an excellent signal quality can beachieved with such a silver-graphite brush on an all-silver slideway.Transition resistance and even contact noise are particularly stable andlow over long service periods. However, the high cost of thisarrangement is a disadvantage. These disadvantages are felt particularlywhen large-size slip rings or slideway arrangements are used, because inthese cases the slideways must be made of solid silver. When, because ofexcessive cost, a less expensive contact material such as brass orcopper is utilized, these less expensive materials have a detrimentaleffect on the electrical transmission characteristics of the system. Thetransition resistance and contact noise may both be higher compared withthe silver array, by up to two orders.

A known method of solving this problem is the application of solid brassslideways which are provided with a silver contact surface. Silverplating can here be made by a mechanical deposition of a silver coatingor even by electrochemical treatment. The disadvantage of such anarrangement resides in the comparatively thin deposited silver layer. Incase of high loads this layer can be worn off after a short time alreadyand the brass slideway then remaining presents again very insufficienttransmission characteristics.

The transmission characteristics of such sliding contacts are usuallycharacterised by a number of electrical parameters. When high currentsare transmitted the transition resistance is of particular importance.This parameter should be very low, preferably within the range of a fewmΩ. Towards lower signal levels, which occur, for instance, in measuringand sensor signals, the contact noise is important as well. Such noiseoccurs during the movement of the contacts as a result of mechanicalvibration, a change of the contact point and additionally on account ofsmall electric arcs which may be formed between the two contactelectrodes. Low contact noise is particularly important for a goodsignal quality.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is based on the problem of providing anarrangement for transmitting electrical signals and/or energy betweenunits mobile relative to each other, by means of galvanic contacts andparticularly a sliding contact arrangement, which will, on the one hand,offer a long service life and a high degree of reliability, even at highcontacting rates, and, on the other hand, ensure an excellent quality insignal transmission.

One inventive solution to this problem is defined in Patent Claim 1.Improvements of the invention are the subject matters of the dependentClaims.

In accordance with the invention, at least one of the contacts presentsa basic material having a high mechanical stability and into which, asecond material that posses good electrical properties for thetransmission of electrical signals and/or energy, is embedded. Thesecond material is distributed in the basic material, so that at leastone further contact that contacts the first contact, is in contact withthe second material along the trajectory of its movement.

The invention hence combines the advantages of two different contactmaterials such as steel, brass or copper and silver. Here, the basicmaterial, which is resistant to wear and inexpensive, serves as carrierof the arrangement whilst the second material, which presents goodelectrical properties, serves as contacting material. Due to thisinventive configuration a particularly high transition quality can beachieved.

The contact consisting of a basic material, with a second materialembedded therein, may be a slideway of a slip ring or contact brush, forinstance.

The second material may be dispersed in the surface of the basicmaterial, alternatively or additionally, the basic material may have atleast one recess in which the second material is embedded. This recessmay be a dovetailed groove, in particular, and with such a positivelocking a particularly good connection is achieved between the twomaterials.

It is moreover expedient that the recess extends obliquely with respectto the sliding direction, in particular with an undulated course, atleast in sections.

According to an alternative, the second material may be embedded in theform of several islets, i.e. contact areas externally separated fromeach other, or in the form of a trajectory in the basic material.

In any case it is advantageous, however, to vary the recess in terms ofits extension or its shape orthogonally to the sliding direction in sucha way that as a result of the contact with the sliding contactconnection traces of the second material are rubbed into the basicmaterial. On account of the sliding motion of the contacts minuteparticles of the second material having the good electrical propertiesare rubbed into the surface of the basic material, i.e. the solidcontact trajectory, where they remain embedded in the surface as aproperly conductive coating. As a result, the conductivity andparticularly the contact noise as well as the transition resistance ofthe entire arrangement are substantially improved.

In yet another embodiment of the present invention, the second materialis selected so that it is softer than the basic material. It can thus beeasily transferred into the surface of the basic material.

It is moreover preferred to support at least one contact element elementwith a certain tolerance in a direction orthagonal on the main slidingdirection. Owing to the small additional movements of the burshtransversely or obliquely to the main axis of movement, the secondcontact material can be better distributed over the contact trajectoryconsisting of the basic material. This may be achieved in a particularlysimple manner by means of a suspension or support with high tolerancespermitting a better bearing clearance. This can, of course, also beachieved by a selective control of the movement with guidance of thecontacts so as to cause them to follow a predetermined trajectory.

In another expedient embodiment of the invention the trajectory of thesecond material is configured in a shape varying from the shape of themain trajectory of the arrangement. This may be a helical trajectory,for instance.

In the contact arrangement described above, which consists of a brushcontaining preferably an electrically conductive material and alubricating material, where a contact trajectory comprises anelectrically conductive material. It is therefore irrelevant whetherthese components are exchanged, i.e. a brush having an electricallyconductive material on a contact trajectory comprising a combination ofan electrically conductive material and a lubricating material such assilver and graphite. In such a case, the inventive arrangement wouldapply for the brush, which now contains two different conductivematerials.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more details in the following by anexemplary embodiment, with reference to the drawing wherein:

FIG. 1 shows an inventive arrangement, and

FIG. 2 illustrates an arrangement including a trajectory of the secondcontact, which is laid in an undulated configuration.

FIG. 3 illustrates the inventive arrangement according to FIG. 1.

FIG. 4 illustrates another inventive arrangement of the presentinvention.

FIG. 5 shows still another inventive arrangement of the presentinvention.

DESCRIPTION OF AN EMBODIMENT

FIG. 1 shows an inventive arrangement consisting of a first contactpartner which, in its turn, includes a basic material or a firstmaterial (1) having good mechanical properties, as well as a slightquantity of a second material (2) having appropriate electricalcharacteristics.

For a better mechanical fixing, the second material is provided in agroove designed in a dovetailed shape. Moreover, a second contactpartner (3) is included which may be a brush, for instance, consistingof silver and graphite. It is irrelevant, of course, whether in thisarrangement the brush consists of silver and graphite or whether thetrajectory as such consists of such a material or whether a brush isrealised with the two aforedescribed contact partners.

FIG. 2 illustrates an arrangement consisting of a first contact material(1) as well as a trajectory of a second contact material (2) which islaid in an undulated configuration therein so that a better distributionof these contact material is achieved throughout the entire surface,particularly of the first material (1).

FIG. 3 illustrates another advantageous embodiment of the presentinvention. A slideway 4 is positioned relative to contact brush 5 suchthat contact brush 5 contacts slideway 4.

FIG. 4 illustrates yet another advantageous embodiment of the presentinvention. A slip ring 8 is coupled with a contact brush 5. The contactbrush 5 comprises a first material 6 having high mechanical hardness anda second material 7 which is electrically conductive. The secondmaterial 7 is deposited in a dovetail shaped groove 9 in the firstmaterial 6. The dovetail shaped groove 9 may comprise an undulatedcourse transversely to the trajectory of movement as depicted in FIG. 2.

FIG. 5 shows an arrangement comprising a first contact material (20) anda trajectory of a second contact material (21). The second contactmaterial (21) is formed as several islets that have an undulatedconfiguration therein so that a better distribution of the contactmaterial is achieved throughout the surface of the first material (20).

What is claimed is:
 1. A system for transmitting electrical signalsand/or energy between units mobile relative to each other through asliding contact arrangement, the system comprising: a slidewaycomprising a first material, said slideway having a recess formed alonga trajectory of movement and an insert having a width (I) and located inthe recess; and a contact, which touches the slideway along a thetrajectory of movement, said contact having a width (L); wherein saidcontact width (L) is greater than said insert width (I) such that saidcontact touches both said first and said second material as it movealong the trajectory of movement and said second material electricallycontacts said first material.
 2. The system according to claim 1,wherein said second material has a lower electrical resistance than thefirst material and the first material has a higher mechanical hardnessthan the second material.
 3. The system according to claim 1, whereinsaid slideway is a component of a slip ring assembly.
 4. The systemaccording to claim 1, wherein said second material is dispersed in thesurface of said first material.
 5. The system according to claim 1,wherein said recess is a dovetail-shaped groove.
 6. The system accordingto claim 1, wherein said second material is arranged in the form of atrajectory along said trajectory of movement.
 7. The system according toclaim 1, wherein said recess varies in its extension or in its shape ina direction orthogonal to the trajectory of movement in such a way that,by the contact of the slideway connection, traces of said secondmaterial are deposited into said first material.
 8. The system accordingto claim 1, wherein said sliding contact arrangement is configured sothat the relative movement of the slideway and the contact takes placealong a varying or non-symmetrical trajectory.
 9. The system accordingto claim 1, wherein at least one further contact region is providedwhich consists of graphite and which lubricates said sliding-contactconnection in sliding motion.
 10. The system according to claim 1,wherein the recess extends obliquely relative to the sliding direction,at least in sections.
 11. The system according to claim 10, wherein saidrecess had an undulated course.
 12. The system according to claim 1,wherein at least one contact element is supported with a tolerance in adirection orthogonal on a main sliding direction.
 13. The systemaccording to claim 12, wherein said contact element is guidedorthogonally on or obliquely relative to the main sliding direction whensaid sliding-contact connection is sliding.
 14. The system according toclaim 1, wherein said second material is selected so that it is softerthan said first material.
 15. The system according to claim 14, whereinsaid first material is steel, copper, a copper or a brass alloy, andthat said second material is silver or a silver alloy.
 16. The systemaccording to claim 1, wherein said second material is embedded into saidfirst material in the form of several islets.
 17. The system accordingto claim 16, wherein said several islets comprise contact areasexternally separated from each other.
 18. A system for transmittingelectrical signals and/or energy between units mobile relative to eachother through a sliding contact arrangement, the system comprising: aslideway comprising a first material, said first material having arecess formed along a trajectory of movement; an insert formed of asecond material deposited in said recess, said insert having a width(I), where said second material has a lower electrical resistance thanthe first material and the first material has a higher mechanicalhardness than the second material and wherein said second materialelectrically contacts said first material; a contact having a width (L);wherein said contact width (L) is greater than said insert width (I)such that the contact, which contacts the slideway along said trajectoryof movement, touches said first and said second material along saidtrajectory of movement.
 19. A system for transmitting electrical signalsand/or energy between units mobile relative to each other through asliding contact arrangement, the system comprising: a slideway; and acontact having a width (L) and comprising a first material, whichcontacts the slideway along a trajectory of movement, and a recesshaving a width (I) formed along the trajectory of movement, the recesshaving an insert located therein and comprising a second material;wherein said contact width (L) is greater than said insert width (I)such that said contact touches both said first and said second materialas it moves along the trajectory of movement and said second materialelectrically contacts said first material.
 20. A system for transmittingelectrical signals and/or energy between units mobile relative to eachother through a sliding contact arrangement, the system comprising: aslip-ring comprising a first material and having a recess formed thereinalong a trajectory of movement; an insert comprising a second materialand located in the recess, said insert having a width (I) that istransverse to the trajectory of movement, and said insert comprises asecond material that electrically contacts the first material; and acontact which contacts said slip-ring along the trajectory of movement,said contact having a width (L) transverse to the trajectory ofmovement; wherein said contact width (L) is greater than said insertwidth (I) such that said contact touches both said first and said secondmaterial as it moves along the trajectory of movement.